tpm: ibmvtpm: Avoid error message when process gets signal while waiting

[ Upstream commit 047d422 ]

When rngd is run as root then lots of these types of message will appear
in the kernel log if the TPM has been configured to provide random bytes:

[ 7406.275163] tpm tpm0: tpm_transmit: tpm_recv: error -4

The issue is caused by the following call that is interrupted while
waiting for the TPM's response.

sig = wait_event_interruptible(ibmvtpm->wq, !ibmvtpm->tpm_processing_cmd);

Rather than waiting for the response in the low level driver, have it use
the polling loop in tpm_try_transmit() that uses a command's duration to
poll until a result has been returned by the TPM, thus ending when the
timeout has occurred but not responding to signals and ctrl-c anymore. To
stay in this polling loop extend tpm_ibmvtpm_status() to return
'true' for as long as the vTPM is indicated as being busy in
tpm_processing_cmd. Since the loop requires the TPM's timeouts, get them
now using tpm_get_timeouts() after setting the TPM2 version flag on the
chip.

To recreat the resolved issue start rngd like this:

sudo rngd -r /dev/hwrng -t
sudo rngd -r /dev/tpm0 -t

Link: https://bugzilla.redhat.com/show_bug.cgi?id=1981473
Fixes: 6674ff1 ("tpm_ibmvtpm: properly handle interrupted packet receptions")
Cc: Nayna Jain <nayna@linux.ibm.com>
Cc: George Wilson <gcwilson@linux.ibm.com>
Reported-by: Nageswara R Sastry <rnsastry@linux.ibm.com>
Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
Tested-by: Nageswara R Sastry <rnsastry@linux.ibm.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/char/tpm/tpm_ibmvtpm.c

@@ -106,17 +106,12 @@ static int tpm_ibmvtpm_recv(struct tpm_chip *chip, u8 *buf, size_t count)
 {
 	struct ibmvtpm_dev *ibmvtpm = dev_get_drvdata(&chip->dev);
 	u16 len;
-	int sig;
 
 	if (!ibmvtpm->rtce_buf) {
 		dev_err(ibmvtpm->dev, "ibmvtpm device is not ready\n");
 		return 0;
 	}
 
-	sig = wait_event_interruptible(ibmvtpm->wq, !ibmvtpm->tpm_processing_cmd);
-	if (sig)
-		return -EINTR;
-
 	len = ibmvtpm->res_len;
 
 	if (count < len) {
@@ -237,7 +232,7 @@ static int tpm_ibmvtpm_send(struct tpm_chip *chip, u8 *buf, size_t count)
 	 * set the processing flag before the Hcall, since we may get the
 	 * result (interrupt) before even being able to check rc.
 	 */
-	ibmvtpm->tpm_processing_cmd = true;
+	ibmvtpm->tpm_processing_cmd = 1;
 
 again:
 	rc = ibmvtpm_send_crq(ibmvtpm->vdev,
@@ -255,7 +250,7 @@ static int tpm_ibmvtpm_send(struct tpm_chip *chip, u8 *buf, size_t count)
 			goto again;
 		}
 		dev_err(ibmvtpm->dev, "tpm_ibmvtpm_send failed rc=%d\n", rc);
-		ibmvtpm->tpm_processing_cmd = false;
+		ibmvtpm->tpm_processing_cmd = 0;
 	}
 
 	spin_unlock(&ibmvtpm->rtce_lock);
@@ -269,7 +264,9 @@ static void tpm_ibmvtpm_cancel(struct tpm_chip *chip)
 
 static u8 tpm_ibmvtpm_status(struct tpm_chip *chip)
 {
-	return 0;
+	struct ibmvtpm_dev *ibmvtpm = dev_get_drvdata(&chip->dev);
+
+	return ibmvtpm->tpm_processing_cmd;
 }
 
 /**
@@ -457,7 +454,7 @@ static const struct tpm_class_ops tpm_ibmvtpm = {
 	.send = tpm_ibmvtpm_send,
 	.cancel = tpm_ibmvtpm_cancel,
 	.status = tpm_ibmvtpm_status,
-	.req_complete_mask = 0,
+	.req_complete_mask = 1,
 	.req_complete_val = 0,
 	.req_canceled = tpm_ibmvtpm_req_canceled,
 };
@@ -550,7 +547,7 @@ static void ibmvtpm_crq_process(struct ibmvtpm_crq *crq,
 		case VTPM_TPM_COMMAND_RES:
 			/* len of the data in rtce buffer */
 			ibmvtpm->res_len = be16_to_cpu(crq->len);
-			ibmvtpm->tpm_processing_cmd = false;
+			ibmvtpm->tpm_processing_cmd = 0;
 			wake_up_interruptible(&ibmvtpm->wq);
 			return;
 		default:
@@ -688,8 +685,15 @@ static int tpm_ibmvtpm_probe(struct vio_dev *vio_dev,
 		goto init_irq_cleanup;
 	}
 
-	if (!strcmp(id->compat, "IBM,vtpm20")) {
+
+	if (!strcmp(id->compat, "IBM,vtpm20"))
 		chip->flags |= TPM_CHIP_FLAG_TPM2;
+
+	rc = tpm_get_timeouts(chip);
+	if (rc)
+		goto init_irq_cleanup;
+
+	if (chip->flags & TPM_CHIP_FLAG_TPM2) {
 		rc = tpm2_get_cc_attrs_tbl(chip);
 		if (rc)
 			goto init_irq_cleanup;

drivers/char/tpm/tpm_ibmvtpm.h

@@ -41,7 +41,7 @@ struct ibmvtpm_dev {
 	wait_queue_head_t wq;
 	u16 res_len;
 	u32 vtpm_version;
-	bool tpm_processing_cmd;
+	u8 tpm_processing_cmd;
 };
 
 #define CRQ_RES_BUF_SIZE	PAGE_SIZE